The present invention relates to an brake fluid pressure generator which combines a master cylinder and a booster of air pressure type used in vehicular braking devices.
As brake fluid pressure generator used in vehicular braking systems, there are conventionally known devices which are provided with a booster of air pressure type having a power piston which is supported by a shell and which moves by means of the differential pressure generated in both sides of power piston, a return spring which is provided between the power piston and the inner end portion of the interlocking portion of the shell which is formed so as to project inward in the direction of movement of the power piston, and an output shaft provided to the moving side of the power piston; and with a master cylinder wherein a single ended opening is inserted into the interlocking portion of the shell, a piston provided internally moves by means of the output of the output shaft to generate brake fluid pressure, and a stopper member for preventing the pulling out of the piston is interlocked with the opening.
In order to shorten the total length of a brake fluid pressure generator of the above described type, it is conceivable to make the projection amount large for the interlocking portion of the shell, and to make the insertion amount of the power piston to the interlocking portion large. However, when the projection amount of the interlocking portion is made large, the setting length of the return spring is shortened. For this mason, the setting of the return spring, which is strict with regard to stress, becomes difficult.
Moreover, an earlier application, Utility Model Application Hei 2-50680, by the present applicant discloses a brake fluid pressure generator designed with the aforementioned objective of shortening total length in mind. This device shortens the total length of the brake fluid pressure generator by projecting the piston of the master cylinder toward the booster of air pressure type side, while leaving as is the amount of projection of the interlocking unchanged portion. Because the projection amount of the interlocking portion is not changed, them is sufficient length for the return spring. However, this is problematic in that the number of parts increase. Accordingly, on this point, them is still room for improvement.